Murkowski said she didn't easily arrive at her decision to reverse her earlier pledge not to mount a write-in campaign, but was swayed by what she claimed were pleas from supporters, her Democratic opponent's inexperience and the bitter taste left by what she called Miller's "last-minute mudslinging" and "outright lies."
"As of last night, I was still wrestling with this," she said. "I looked into my heart and I said, 'Where is my heart?' And my heart is Alaska. I cannot leave you. I cannot stop what we have started, what Ted [the late Sen. Ted Stevens, R-Alaska] and so many others have built and we are advancing."
Murkowski made the announcement after inviting members of the media to photograph the event without officially revealing its nature.
However, the Anchorage Daily News reported that Murkowski campaign staff member Bonnie Jack sent out an e-mail asking people to "join us at the Kick-off of Senator Lisa's campaign" and "write in her name in and fill in the oval" on Election Day.
"We plan to make history!" the invitation read, according to the newspaper.
The Anchorage Daily News also cited a Facebook post from Murkowski's cousin, Mary Gore: "My cousin will announce at 5:00 today that she will run as a write-in candidate for US Senate. GO LISA GO! ... Come be a part of history AND learn how to spell her last name correctly for the ballot!"
Republican insiders blamed Murkowski's loss on her not taking Miller's threat seriously enough. One Republican strategist said that Murkowski's campaign was advised 10 weeks ago to use her huge monetary funds to attack Miller, but did not heed the advice, to her peril.
Instead, she targeted President Obama and touted her work in helping Alaskans. It was only on Aug. 23 -- a day before the elections -- that she finally went up with a negative radio ad against Miller. At that point, it was too late.
"I will be the first one to admit to you that we made some mistakes," she told her supporters Friday. "When he swung, I didn't swing back."
Her write-in campaign will be different, she insisted.
"The gloves are off," she said. "I'm fighting for Alaska. We're in."
Miller, once a virtual unknown, was propelled by an aggressive campaign attacking Murkowski's voting record in Washington and high-profile endorsements from former Arkansas Gov. Mike Huckabee, former Alaska Gov. Sarah Palin and the California-based Tea Party Express.
Murkowski also took a beating for being too soft on abortion, a hot-button issue among conservatives. Miller's campaign accused the incumbent senator of not being pro-life. But Murkowski didn't fight back until very late or make any of the issues a focal point of her campaign, giving her opponents free rein on what they could say.
Perhaps another political shift that Murkowski didn't see coming was the power of Palin's endorsement and the Tea Party's influence, one that, many say, helped change the course of the race.
Unlike some of her "mama grizzlies," Palin remained behind the scenes in Miller's campaign. She didn't appear in any TV ads or at rallies for him, and only recorded one robocall toward the end.
But it was Palin, Republican insiders said, who helped pull the purse strings. Her political action committee gave $5,000 to Miller's campaign and helped with getting the Tea Party Express to bankroll much of it.